/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package datafu.hourglass.mapreduce;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.Reducer;

/**
 * A Hadoop reducer which delegates to an implementation read from the distributed cache.
 * 
 */
public class DelegatingReducer extends Reducer<Object, Object, Object, Object> 
{
  private ObjectReducer processor;
  
  @Override
  protected void setup(Context context) throws java.io.IOException, java.lang.InterruptedException
  {
    super.setup(context);
    
    if (context != null)
    {
      Configuration conf = context.getConfiguration();
      
      String path = conf.get(Parameters.REDUCER_IMPL_PATH);
      
      this.processor = (ObjectReducer)DistributedCacheHelper.readObject(conf, new Path(path));
      this.processor.setContext(context);
    }
  }
  
  @Override
  protected void reduce(Object key, Iterable<Object> values, Context context) throws java.io.IOException, java.lang.InterruptedException
  {
    this.processor.reduce(key, values, context);
  }

  @Override
  protected void cleanup(Context context) throws IOException,
      InterruptedException
  {
    this.processor.close();
  }
}
